Radio link control

ABSTRACT

The invention relates to apparatuses, methods, a system, computer programs, computer program products and computer-readable media.

FIELD

The invention relates to apparatuses, methods, a system, computerprograms, computer program products and computer-readable media.

BACKGROUND

The following description of background art may include insights,discoveries, understandings or disclosures, or associations togetherwith disclosures not known to the relevant art prior to the presentinvention but provided by the invention. Some such contributions of theinvention may be specifically pointed out below, whereas other suchcontributions of the invention will be apparent from their context. Incommunication systems, latency control is one of key issues in achievingthe best possible operation.

BRIEF DESCRIPTION

According to an aspect of the present invention, there is provided anapparatus comprising: at least one processor and at least one memoryincluding a computer program code, the at least one memory and thecomputer program code configured to, with the at least one processor,cause the apparatus at least to: assign data to at least one data unitand set a sequence number to the at least one data unit; form aplurality of segments from the at least one data unit, each one of theplurality of segments having the set sequence number as its sequencenumber, and convey the plurality of segments and the sequence numbers toa target entity as an earliest data conveyance by using at least onecomponent carrier.

According to yet another aspect of the present invention, there isprovided a method comprising: assigning data to at least one data unitand set a sequence number to the at least one data unit; forming aplurality of segments from the at least one data unit, each one of theplurality of segments having the set sequence number as its sequencenumber, and conveying the plurality of segments and the sequence numbersto a target entity as an earliest data conveyance by using at least onecomponent carrier.

According to yet another aspect of the present invention, there isprovided an apparatus comprising: means for assigning data to at leastone data unit and set a sequence number to the at least one data unit;means for forming a plurality of segments from the at least one dataunit, each one of the plurality of segments having the set sequencenumber as its sequence number, and means for conveying the plurality ofsegments and the sequence numbers to a target entity as an earliest dataconveyance by using at least one component carrier.

According to yet another aspect of the present invention, there isprovided a computer program embodied on a computer-readable storagemedium, the computer program comprising program code for controlling aprocess to execute a process, the process comprising: assigning data toat least one data unit and set a sequence number to the at least onedata unit; forming a plurality of segments from the at least one dataunit, each one of the plurality of segments having the set sequencenumber as its sequence number, and conveying the plurality of segmentsand the sequence numbers to a target entity as an earliest dataconveyance by using at least one component carrier.

LIST OF DRAWINGS

Some embodiments of the present invention are described below, by way ofexample only, with reference to the accompanying drawings, in which

FIG. 1 illustrates an example of a system;

FIG. 2 is a flow chart, and

FIG. 3 illustrates examples of an apparatus.

DESCRIPTION OF EMBODIMENTS

The following embodiments are only examples. Although the specificationmay refer to “an”, “one”, or “some” embodiment(s) in several locations,this does not necessarily mean that each such reference is to the sameembodiment(s), or that the feature only applies to a single embodiment.Single features of different embodiments may also be combined to provideother embodiments.

Embodiments are applicable to any user device, such as a user terminal,relay node, server, node, corresponding component, and/or to anycommunication system or any combination of different communicationsystems that support required functionalities. The communication systemmay be a wireless communication system or a communication systemutilizing both fixed networks and wireless networks. The protocols used,the specifications of communication systems, apparatuses, such asservers and user terminals, especially in wireless communication,develop rapidly. Such development may require extra changes to anembodiment. Therefore, all words and expressions should be interpretedbroadly and they are intended to illustrate, not to restrict,embodiments.

In the following, different exemplifying embodiments will be describedusing, as an example of an access architecture to which the embodimentsmay be applied, a radio access architecture based on LTE Advanced,LTE-A, that is based on orthogonal frequency multiplexed access (OFDMA)in a downlink and a single-carrier frequency-division multiple access(SC-FDMA) in an uplink, without restricting the embodiments to such anarchitecture, however. It is obvious for a person skilled in the artthat the embodiments may also be applied to other kinds ofcommunications networks having suitable means by adjusting parametersand procedures appropriately. For example, the embodiments areapplicable to both frequency division duplex (FDD) and time divisionduplex (TDD).

In an orthogonal frequency division multiplexing (OFDM) system, theavailable spectrum is divided into multiple orthogonal sub-carriers. InOFDM systems, available bandwidth is divided into narrower sub-carriersand data is transmitted in parallel streams. Each OFDM symbol is alinear combination of signals on each of the subcarriers. Further, eachOFDM symbol is preceded by a cyclic prefix (CP), which is used todecrease Inter-Symbol Interference. Unlike in OFDM, SC-FDMA subcarriersare not independently modulated.

Typically, a (e)NodeB (“e” stands for evolved) needs to know channelquality of each user device and/or the preferred precoding matrices(and/or other multiple input-multiple output (MIMO) specific feedbackinformation, such as channel quantization) over the allocated sub-bandsto schedule transmissions to user devices. Required information isusually signalled to the (e)NodeB.

FIG. 1 depicts examples of simplified system architectures only showingsome elements and functional entities, all being logical units, whoseimplementation may differ from what is shown. The connections shown inFIG. 1 are logical connections; the actual physical connections may bedifferent. It is apparent to a person skilled in the art that the systemtypically comprises also other functions and structures than those shownin FIG. 1.

The embodiments are not, however, restricted to the system given as anexample but a person skilled in the art may apply the solution to othercommunication systems provided with the necessary properties. Someexamples of other options for suitable systems are the universal mobiletelecommunications system (UMTS) radio access network (UTRAN orE-UTRAN), long term evolution (LTE, the same as E-UTRA), wireless localarea network (WLAN or WiFi), worldwide interoperability for microwaveaccess (WiMAX), Bluetooth®, personal communications services (PCS),ZigBee®, wideband code division multiple access (WCDMA), systems usingultra-wideband (UWB) technology, sensor networks, mobile ad-hoc networks(MANETs) and Internet Protocol multimedia subsystems (IMS).

FIG. 1 shows a part of a radio access network of E-UTRA, LTE,LTE-Advanced (LTE-A) or LTE/EPC (EPC=evolved packet core, EPC isenhancement of packet switched technology to cope with faster data ratesand growth of Internet protocol traffic). E-UTRA is an air interface ofRelease 8 (UTRA=UMTS terrestrial radio access, UMTS=universal mobiletelecommunications system). Some advantages obtainable by LTE (orE-UTRA) are a possibility to use plug and play devices, and FrequencyDivision Duplex (FDD) and Time Division Duplex (TDD) in the sameplatform.

FIG. 1 shows user devices 100 and 102 configured to be in a wirelessconnection on one or more communication channels 104, 106 in a cell witha (e)NodeB 108 providing the cell. The physical link from a user deviceto a (e)NodeB is called uplink or reverse link and the physical linkfrom the NodeB to the user device is called downlink or forward link.

The NodeB, or advanced evolved node B (eNodeB, eNB) in LTE-Advanced, isa computing device configured to control the radio resources ofcommunication system it is coupled to. The (e)NodeB may also be referredto a base station, an access point or any other type of interfacingdevice including a relay station capable of operating in a wirelessenvironment.

The (e)NodeB includes transceivers, for entity. From the transceivers ofthe (e)NodeB, a connection is provided to an antenna unit thatestablishes bi-directional radio links to user devices. The antenna unitmay comprise a plurality of antennas or antenna elements. The (e)NodeBis further connected to core network 110 (CN). Depending on the system,the counterpart on the CN side can be a serving gateway (S-GW, routingand forwarding user data packets), packet data network gateway (P-GW),for providing connectivity of user devices (UEs) to external packet datanetworks, or mobile management entity (MME), etc.

A communications system typically comprises more than one (e)NodeB inwhich case the (e)NodeBs may also be configured to communicate with oneanother over links, wired or wireless, designed for the purpose. Theselinks may be used for signalling purposes.

The communication system is also able to communicate with othernetworks, such as a public switched telephone network or the Internet112.

The user device (also called UE, user equipment, user terminal, etc.)illustrates one type of an apparatus to which resources on the airinterface are allocated and assigned, and thus any feature describedherein with a user device may be implemented with a correspondingapparatus, such as a relay node. An example of such a relay node is alayer 3 relay (self-backhauling relay) towards the base station.

The user device typically refers to a portable computing device thatincludes wireless mobile communication devices operating with or withouta subscriber identification module (SIM), including, but not limited to,the following types of devices: a mobile station (mobile phone),smartphone, personal digital assistant (PDA), handset, device using awireless modem (alarm or measurement device, etc.), laptop and/or touchscreen computer, tablet, game console, notebook, and multimedia device.

The user device (or in some embodiments a layer 3 relay node) isconfigured to perform one or more of user equipment functionalities. Theuser device may also be called a subscriber unit, mobile station, remoteterminal, access terminal, user terminal or user equipment (UE) just tomention but a few names or apparatuses.

It should be understood that, in FIG. 1, user devices are depicted toinclude 2 antennas only for the sake of clarity. The number of receptionand/or transmission antennas may naturally vary according to a currentimplementation. Further, although the apparatuses have been depicted assingle entities, different units, processors and/or memory units (notall shown in FIG. 1A) may be implemented.

It is obvious for a person skilled in the art that the depicted systemis only an example of a part of a radio access system and in practise,the system may comprise a plurality of (e)NodeBs, the user device mayhave an access to a plurality of radio cells and the system may comprisealso other apparatuses, such as physical layer relay nodes or othernetwork elements, etc. At least one of the NodeBs or eNodeBs may be aHome(e)nodeB. Additionally, in a geographical area of a radiocommunication system a plurality of different kinds of radio cells aswell as a plurality of radio cells may be provided. Radio cells may bemacro cells (or umbrella cells) which are large cells, usually having adiameter of up to tens of kilometres, or smaller cells such as micro-,femto- or picocells. The (e)NodeB 108 of FIG. 1 may provide any kind ofthese cells. A cellular radio system may be implemented as a multilayernetwork including several kinds of cells. Typically, in multilayernetworks, one node B provides one kind of a cell or cells, and thus aplurality of node Bs are required to provide such a network structure.

The LTE-Advanced is targeted to provide even higher peak-data rates thanthe LTE. These are achievable with an increase of transmissionbandwidth. The transmission bandwidth can be increased whilesimultaneously maintaining the spectral compatibility with LTE devices(an LTE-Advanced capable network is designed to appear as an LTE networkfor an LTE user device) by carrier aggregation, wherein multiple LTEcomponent carriers (typically LTE Release 8 carriers) are aggregated ona medium access control (MAC) layer to provide required bandwidth. Theaggregation of component carriers may be carried out at differentprotocol layers. An LTE user device sees each component carrier as anLTE carrier, whereas an LTE-Advanced user device is able to exploit theaggregated bandwidth as a whole. LTE user devices receive or transmit onone component carrier, whereas LTE-advanced user devices may receive ortransmit on multiple component carriers simultaneously to reach higherbandwidths. When carrier aggregation is used, a single radio linkcontrol (RLC) protocol entity is usually used per a user device insteadof carrier-specific RLC protocol entities.

A Release 8 transmission chain on a physical layer typically consists ofsegmentation of transport blocks obtained from higher layers (MediaAccess Control, MAC) into code blocks, turbo coding of each code blockand attaching a Cyclic Redundancy Check to the codes blocks andtransport blocks, modulating, layer mapping for diversity transmissionor spatial multiplexing, and pre-coding and mapping onto physicalresource blocks.

The Long Term Evolution (LTE) Layer 2 user-plane protocol stackgenerally comprises three sub-layers: the packet data convergenceprotocol (PDCP) layer, the radio link control (RLC) layer, and themedium access control (MAC) layer. Usually, the PDCP layer (on the topof the protocol stack) processes radio resource control (RRC) messageson the control plane and Internet Protocol (IP) packets on the userplane. Depending on the type of a radio bearer, main functions of thePDCP layer may be header compression, security, and support forreordering and retransmission during handover.

Typically, the RLC layer (a middle layer of the protocol stack) providessegmentation and/or reassembly of upper layer packets in order to adaptthem to a size suitable for radio interface. The RLC layer may alsocarry out retransmission in the case of packet losses. Additionally, theRLC layer may carry out reordering to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ) operation in themedia access control (MAC) layer.

The MAC layer (bottom one of the protocol stack) is designed to carryout multiplexing of data from different radio bearers.

For data transmission, the RLC layer may receive packets from the packetdata convergence protocol (PDCP) layer. These packets are typicallycalled PDCP protocol data units (PDUs) when considered from the PDCPlayer's perspective and represent RLC service data units (SDUs) from theRLC layer's point of view. The RLC layer may provide suitable packets tothe layer below which typically is the MAC layer. The packets the RLCprovides the MAC layer with are RLC PDUs when considered from the RLClayer's side and MAC SDUs from the MAC layer's point of view.

The RLC layer may process SDUs in a plurality of ways: it may produceone PDU of a plurality of SDUs or it may carry out segmentation that is“split” an SDU in such a manner that different parts of an SDU end up indifferent PDUs.

In this application, an entity providing services of the RLC layer iscalled an RLC entity or a logical RLC entity. An embodiment relates toradio link control (RLC) protocol in E-UTRAN [3GPP TS 36.322].

Typically, the RLC layer provides segmentation and/or concatenation ofupper layer packets in order to adapt them to a size suitable for thesize of a MAC service data unit (SDU) which in turn depends on the sizeof a current transport block of a physical layer. For carrying outretransmission, a resegmentation may be needed, since the transportblock size and/or MAC SDU size may have been changed.

Usually, the RLC protocol presents two PDU formats for the transfer ofhigher-layer data, such as RLC service data units (SDUs): anacknowledged mode data (AMD) protocol data unit (PDU) and an AMD PDUsegment. In the protocol, an AMD PDU is used to transfer upper layerPDUs by an acknowledged mode (AM) RLC entity. It is used when the AM RLCentity transmits (at least a part of) the RLC SDU for the first time, orwhen the AM RLC entity retransmits an AMD PDU without performingre-segmentation. An AMD PDU segment is used to transfer upper layer PDUsby an AM RLC entity. It is used when the AM RLC entity needs toretransmit a portion of an AMD PDU. Thus, AMD PDU segments are typicallyformed by resegmentation of parts of an original AMD PDU needed forretransmission. On the MAC layer, these AMD PDU segments are seen as MACSDUs of which the MAC layer forms one or more MAC PDUs the size of whichis determined based on the size of a transport block on a physicallayer.

In the following, some embodiments are disclosed in further details inrelation to FIG. 2. The embodiment of FIG. 2 is usually related to abase station, node, host, server and/or user device. The embodimentstarts in block 200. An embodiment is especially suitable for carryingout preassignment of higher-layer data to a component carrier withoutknowing beforehand the size of MAC PDUs or other corresponding dataunits that are going to be scheduled.

In block 202, data is assigned to at least one data unit and a sequencenumber is set to the at least one data unit.

Data units may be protocol data units (PDUs). In a layered communicationsystem, such as a system based on open system interconnection (OSI)model, a data unit is usually specified in a protocol of a layer inquestion.

The Long Term Evolution (LTE), which is herein used as an example of acommunication system, Layer 2 user-plane protocol stack generallycomprises three sub-layers: a packet data convergence protocol (PDCP)layer, a radio link control (RLC) layer, and a medium access control(MAC) layer. Data packets are typically called PDCP protocol data units(PDUs) when considered from the PDCP layer's perspective and representRLC service data units (SDUs) from the RLC layer's point of view. A PDCPPDU and/or RLC SDU are examples of data units in a general case.

Assigning data to one or more data units may be carried out by using RLCconcatenation and segmentation mechanisms defined in the 3rd generationpartnership project (3GPP) specification, when a data unit typicallycorresponds to an RLC acknowledged mode data (AMD) protocol data unit(PDU). However, it should be understood that an RLC AMD PDU may notdirectly be conveyed as a MAC SDU.

Typically, every data unit to be conveyed is given a sequence number. Ifeach data unit is individually sequence numbered, each of them may beacknowledged individually. Sequence number space is typically limitedand the sequence numbers are reused. However, the sequence number spaceis usually defined to be large enough that the reusing does not causeacknowledgement errors.

Even though the size of a data unit is typically chosen taking intoaccount the size of a MAC SDU, it is possible that the size of a dataunit is chosen to be larger than the typical size of a MAC SDU requestedby a MAC layer. In this manner it is possible to reduce the propagationrate of an RLC window. Yet another option is that the size of the dataunit is set without taking into account the size of a MAC SDU. In block204, a plurality of segments are formed from the at least one data unit,each one of the plurality of segments having the set sequence number asits sequence number.

In an embodiment, a data unit is given a sequence number which is thenalso given to segments which are formed from this data unit. Segmentsformed from another data unit have the sequence number of that dataunit. In this manner, segments of a data unit may be linked to this“original” data unit.

Forming at least one data unit into segments may be carried out by usingRLC resegmentation mechanism defined in the 3GPP specification toconstruct one or more data unit segments, in which case a segment is oris correspondent to an RLC AMD PDU segment. Segment size may be based onthe size of a service data unit (SDU) requested by a medium accesscontrol (MAC) layer. Segments may be produced one at a time and datapossibly remained from a data unit may be saved for a following segmentto be formed for a following MAC SDU.

An RLC layer may process SDUs in a plurality of ways: it may produce onePDU of a plurality of SDUs or it may carry out segmentation that is“split” an SDU in such a manner that different parts of an SDU end up indifferent PDUs. This processing may be carried out by a master logicalRLC entity or by a slave logical RLC entity, if such a division isapplied.

At least one data unit, such as a PDU, may be formed into segmentscarried by RLC AMD PDU segments, such that the segments forming the atleast one AMD PDU and hence having the same sequence number may also betransmitted on different frequency carriers.

In carrier aggregation, for determining the range of a sequence number,it has to be considered how the possibility of a need of a transmittingRLC entity to stop transmission for waiting for acknowledgements of PDUsfrom a receiving entity may be minimized. It should be understood, thatthe maximum rate of RLC sequence numbering progressing may be divided bythe number of carriers. The maximizing of the size of chosen data unitsusually minimizes the rate of a RLC sequence number (SN) space usage.Thus, a possibility to improve the usage of a sequence number space isprovided. This may be a motivation for the use of RLC AMD PDU segmentsalso for initial transmissions.

If segments carried by AMD PDU segments are used, in maximizing the sizeof data units, the limiting factor becomes a segment offset (SO) field.A segment offset (SO) field indicates the position of the AMD PDUsegment in bytes within the original AMD PDU. Specifically, the SO fieldindicates the position within the data field of the original AMD PDU towhich the first byte of the data field of the AMD PDU segmentcorresponds to.

An RLC reordering timer may be used at a receiving RLC entity toindicate that MAC-layer retransmissions of an RLC PDU are completed. Inone embodiment, an initial transmission of a data unit may span severalcarriers but only within one subframe, i.e. an initial transmission of adata unit may only be segmented in frequency but not in time.

If an initial transmission of a data unit is segmented also in time, asafety margin in the configuration of the expiry value of RLC reorderingtimer may be applied possibly combined with scheduling restrictions,such as giving a higher priority for transmissions of the rest of thesegments of a data unit of which one or more segments have already beentransmitted and/or giving an upper limit for an allowable time betweentransmissions of segments having a same sequence number that is to saybelonging to a same data unit. Another option is that time-segmentationis prohibited only in the uplink, because a user device typically has nocontrol over scheduling.

Additionally, downlink RLC AMD PDU segments may be constructed when thetransport block size has been determined by packet scheduling and linkadaptation functionalities

In block 206, the plurality of segments and the sequence numbers areconveyed to a target entity as an earliest data conveyance by using atleast one component carrier.

In one embodiment, segments formed from one data unit are conveyed byusing one component carrier, but different data units and/or segmentsmade of them may be conveyed on different component carriers. In anotherembodiment, segments formed from one data unit are conveyed at leastpartly on different component carriers. Segments having the samesequence number may be conveyed on different frequency carriers orduring several subframes on one component carrier.

Conveying may mean sending, transmitting or submitting to a lowerprotocol layer for transmission, for example. In practice, the earliestdata conveyance may be carried out as one conveyance event, a sequenceof conveyance events or by a plurality of separate conveyance events.

As to physical layer transmission, it should be understood thatdifferent segments are typically not conveyed as one physical layertransmission. Separate transmissions are used especially when thesegments are transmitted on a same carrier but in different subframes.

At least one segment formed from a data unit, such as an AMD PDU segmentadapted for transmission using carrier aggregation, may be conveyed. Theearliest data conveyance herein means an original or initial dataconveyance, not retransmission.

In an embodiment, more than one component carriers are used and thuscarrier aggregation principle may be applied. Carrier aggregationtypically means aggregation of multiple component carriers for creatinga wider effective bandwidth. Component carriers in different frequencybands may also be aggregated. In the LTE, component carriers can beaggregated to support wider transmission bandwidths up to 100 MHz.Spectrum deployment may be contiguous or non-contiguous.

Typically, a Layer 1 and packet scheduling processing for differentcarriers is physically distributed in nodes, whereas RLC processing iscentralized user device-specifically. Thus latency-criticalcommunication between carrier-specific packet schedulers, a userdevice-specific RLC protocol entity and carrier-specific Layer 1processing is typically needed. Thus latency may be even more criticalwith carrier aggregation.

In carrier aggregation, one component carrier may be a master componentcarrier and other carriers may be slave carriers. A master logical radiolink control (RLC) entity and at least one slave logical radio linkcontrol entity may operate on the carriers. When carrier aggregation isused, a master logical radio link control entity usually takes care ofone carrier, and slave logical radio link control entities may take careof other carriers used for a same user device. The number of slavelogical radio link control entities thus usually depends on the numberof component carriers used for carrier aggregation.

In an embodiment, a master logical radio link control entity operatingon a master component carrier of a plurality of component carriers andat least one slave logical radio link control entity operating on atleast one slave component carrier of the plurality of component carriersare determined. The at least one slave logical radio link control entitystores a data unit until a segment size is determined and carries outforming segments of the data unit. The logical radio link controlentities form a radio link control (RLC) entity defined in the 3GPPspecification.

A single peer RLC entity is typically visible to each RLC entity in auser device, but physically a network-side entity may be composed of one“master” entity and a number of “slave” entities. The master logical RLCprotocol entity may physically be co-located with one (or more) of thecarriers used for the user device (typically this would be the primarycarrier). The “slave” logical RLC entities in turn may be colocated withother carriers used for the same user device. Term “master entity”typically may mean an entity which at least partly controls “slaveentities” allocated to its control.

The “master” logical RLC entity may take care of maintaining the orderof RLC SDUs and sequence numbering of RLC acknowledged mode data (AMD)PDUs. An RLC AMD PDU may be constructed by taking one or more SDUs froma transmission buffer, performing segmentation and/or concatenation andadding a header. An AMD PDU is usually used to transfer upper layer PDUsby an acknowledge mode (AM) RLC entity.

For transmitting data on other carriers, a master logical RLC entity mayassign a sequence number and convey it together with a data unitincluding one or more RLC SDUs and/or RLC PDU/SDU segments to a slavelogical RLC entity. It should be understood that data units are notimmediately sent to a user device, but instead, to the slave logical RLCentity typically located in a node.

On a slave logical entity, the at least one data unit, such as at leastone RLC AMD PDU, may be buffered until a packet scheduling decision ismade (on a lower level) and the size of a current transport block andthe size of a current MAC SDU are known. After that, the slave logicalRLC entity may utilize the RLC resegmentation mechanism defined in the3GPP specification to form at least one segment from the at least onedata unit. The segment size typically matches a MAC SDU size requestedby a MAC layer. In this case, the segment is an RLC AMD PDU segment.Data possibly remained from a data unit may be saved for a followingsegment to be formed for a following MAC SDU. Some other options forreorganizing data units also exist, such as producing one output dataunit of a plurality of input data units.

In one embodiment, an initial transmission of a data unit may spanseveral carriers but only within one subframe, i.e. an initialtransmission of a data unit may only be segmented in frequency but notin time. If a concept of a master and slave RLC logical entity(ies) isutilized, this may require the master logical RLC entity to assign andconvey a data unit to the slave logical RLC entity that is to say notonly an RLC sequence number but also a segment offset range to beapplied to AMD PDU segment(s).

In case a need for retransmission of one or more RLC PDUs or RLC PDUsegments based on acknowledgement feedback from a logical RLC entityexists, a plurality of possibilities for retransmission exists. Oneoption is that any RLC (acknowledgement/non-acknowledgement) Ack/Nackfeedback (STATUS PDU) is forwarded from a master logical RLC entity tothe same slave logical RLC entity that made the original transmissionand the slave logical RLC entity carries out required retransmissions.

Another possibility is that a master logical RLC entity processes an RLCAck/Nack feedback received from a user device and conveys the requestfor retransmissions to any slave logical RLC entity that is to say notnecessarily the same that was responsible for the original transmission.

Yet another option is that the master logical RLC entity itself performsRLC retransmission using its own carrier.

It is also possible to use different combinations of the options listedabove, especially the combination of second and third options.

Additionally, load balancing between carriers may be based on anon-latency critical flow control algorithm and/or the size of a dataunit may be fixed or it may be predicted by the aid of a slow adaptationalgorithm.

The embodiment ends in block 208. The embodiment is repeatable in manyways. One example is shown by arrow 210 in FIG. 2.

The steps/points, signaling messages and related functions describedabove in FIG. 2 are in no absolute chronological order, and some of thesteps/points may be performed simultaneously or in an order differingfrom the given one. Other functions can also be executed between thesteps/points or within the steps/points and other signaling messagessent between the illustrated messages. Some of the steps/points or partof the steps/points can also be left out or replaced by a correspondingstep/point or part of the step/point.

It should be understood that conveying, transmitting and/or receivingmay herein mean preparing a data conveyance, transmission and/orreception, preparing a message to be conveyed, transmitted and/orreceived, or physical transmission and/or reception itself, etc on acase by case basis.

An embodiment provides an apparatus which may be any node, host, server,user device or any other suitable apparatus capable to carry ourprocesses described above in relation to FIG. 2.

FIG. 3 illustrates a simplified block diagram of an apparatus accordingto an embodiment especially suitable for radio link control.

As an example of an apparatus according to an embodiment, it is shown anapparatus 300, such as a node device, host, server or user device,including facilities in a control unit 304 (including one or moreprocessors, for example) to carry out functions of embodiments, such asforming a plurality of segments from the at least one data unit, eachone of the plurality of segments having the sequence number if a dataunit as its sequence number.

This is depicted in FIG. 3. Block 306 includes parts/units/modules needfor reception and transmission, usually called a radio front end,RF-parts, radio parts, etc. Another example of an apparatus 300 mayinclude at least one processor 304 and at least one memory 302 includinga computer program code, the at least one memory and the computerprogram code configured to, with the at least one processor, cause theapparatus at least to: assign data to at least one data unit and set asequence number to the at least one data unit; form a plurality ofsegments from the at least one data unit, each one of the plurality ofsegments having the set sequence number as its sequence number, andconvey the plurality of segments and the sequence numbers to a targetentity as an earliest data conveyance by using at least one componentcarrier.

Yet another example of an apparatus comprises means 304 for assigningdata to at least one data unit and set a sequence number to the at leastone data unit; means 304 for forming a plurality of segments from the atleast one data unit, each one of the plurality of segments having theset sequence number as its sequence number, and means 304 for conveyingthe plurality of segments and the sequence numbers to a target entity asan earliest data conveyance by using at least one component carrier.

Yet another example of an apparatus comprises an assigner configured toassign data to at least one data unit and set a sequence number to theat least one data unit; a forming unit configured to form a plurality ofsegments from the at least one data unit, each one of the plurality ofsegments having the set sequence number as its sequence number, and aconveying unit configured to convey the plurality of segments and thesequence numbers to a target entity as an earliest data conveyance byusing at least one component carrier. It should be understood that theapparatuses may include or be coupled to other units or modules etc,such as radio parts or radio heads, used in or for transmission and/orreception. This is depicted in FIG. 3 as an optional block 306.

Although the apparatuses have been depicted as one entity in FIG. 3,different modules and memory may be implemented in one or more physicalor logical entities.

An apparatus may in general include at least one processor, controlleror a unit designed for carrying out control functions operably coupledto at least one memory unit and to various interfaces. Further, thememory units may include volatile and/or non-volatile memory. The memoryunit may store computer program code and/or operating systems,information, data, content or the like for the processor to performoperations according to embodiments. Each of the memory units may be arandom access memory, hard drive, etc. The memory units may be at leastpartly removable and/or detachably operationally coupled to theapparatus. The memory may be of any type suitable for the currenttechnical environment and it may be implemented using any suitable datastorage technology, such as semiconductor-based technology, flashmemory, magnetic and/or optical memory devices. The memory may be fixedor removable.

The apparatus may be a software application, or a module, or a unitconfigured as arithmetic operation, or as a program (including an addedor updated software routine), executed by an operation processor.Programs, also called program products or computer programs, includingsoftware routines, applets and macros, can be stored in anyapparatus-readable data storage medium and they include programinstructions to perform particular tasks. Computer programs may be codedby a programming language, which may be a high-level programminglanguage, such as objective-C, C, C++, Java, etc., or a low-levelprogramming language, such as a machine language, or an assembler.

Modifications and configurations required for implementing functionalityof an embodiment may be performed as routines, which may be implementedas added or updated software routines, application circuits (ASIC)and/or programmable circuits. Further, software routines may bedownloaded into an apparatus. The apparatus, such as a node device, or acorresponding component, may be configured as a computer or amicroprocessor, such as single-chip computer element, or as a chipset,including at least a memory for providing storage capacity used forarithmetic operation and an operation processor for executing thearithmetic operation.

Embodiments provide computer programs embodied on a distribution medium,comprising program instructions which, when loaded into electronicapparatuses, constitute the apparatuses as explained above.

Other embodiments provide computer programs embodied on a computerreadable medium, configured to control a processor to performembodiments of the methods described above.

The computer program may be in source code form, object code form, or insome intermediate form, and it may be stored in some sort of carrier,distribution medium, or computer readable medium, which may be anyentity or device capable of carrying the program. Such carriers includea record medium, computer memory, read-only memory, electrical carriersignal, telecommunications signal, and software distribution package,for example. Depending on the processing power needed, the computerprogram may be executed in a single electronic digital computer or itmay be distributed amongst a number of computers.

The techniques described herein may be implemented by various means. Forexample, these techniques may be implemented in hardware (one or moredevices), firmware (one or more devices), software (one or moremodules), or combinations thereof. For a hardware implementation, theapparatus may be implemented within one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described herein, or a combination thereof. Forfirmware or software, the implementation can be carried out throughmodules of at least one chip set (e.g., procedures, functions, and soon) that perform the functions described herein. The software codes maybe stored in a memory unit and executed by processors. The memory unitmay be implemented within the processor or externally to the processor.In the latter case it can be communicatively coupled to the processorvia various means, as is known in the art. Additionally, the componentsof systems described herein may be rearranged and/or complimented byadditional components in order to facilitate achieving the variousaspects, etc., described with regard thereto, and they are not limitedto the precise configurations set forth in the given figures, as will beappreciated by one skilled in the art.

It will be obvious to a person skilled in the art that, as technologyadvances, the inventive concept may be implemented in various ways. Theinvention and its embodiments are not limited to the examples describedabove but may vary within the scope of the claims.

The invention claimed is:
 1. An apparatus comprising: at least oneprocessor and at least one memory including a computer program code, theat least one memory and the computer program code configured to, withthe at least one processor, cause the apparatus at least to: assign datato at least one data unit and set a sequence number to the at least onedata unit; form a plurality of segments from the at least one data unit,each one of the plurality of segments having the set sequence number asits sequence number, convey the plurality of segments and the sequencenumbers to a target entity as an earliest data conveyance by using atleast one component carrier; and determine a master logical radio linkcontrol entity operating on a master component carrier of a plurality ofcomponent carriers and at least one slave logical radio link controlentity operating on at least one slave component carrier of theplurality of component carriers, wherein the at least one slave logicalradio link control entity is configured to store the at least one dataunit until a segment size is selected and thereafter to form theplurality of segments.
 2. The apparatus of claim 1, wherein the forminga plurality of segments is based on acknowledged mode data (AMD)protocol data unit (PDU) resegmentation.
 3. The apparatus of claim 2,wherein radio link control (RLC) acknowledged mode data (AMD) protocoldata unit (PDU) segments having a same sequence number are conveyed ondifferent frequency carriers.
 4. The apparatus of claim 3, wherein theradio link control (RLC) acknowledged mode data (AMD) protocol data unit(PDU) segments having the same sequence number are conveyed during onesubframe.
 5. The apparatus of claim 2, wherein radio link control (RLC)acknowledged mode data (AMD) protocol data unit (PDU) segments having asame sequence number are conveyed during several subframes on onecomponent carrier.
 6. The apparatus of claim 1, wherein the logicalradio link control entities form a radio link control (RLC) entitydefined in the 3rd generation partnership project (3GPP) specification.7. The apparatus of claim 1, the apparatus comprising a server, host,node or user device.
 8. The apparatus of claim 1, further configured toselect the segment size based on a service data unit (SDU) sizerequested by a medium access control (MAC) layer.
 9. A methodcomprising: assigning data to at least one data unit and setting asequence number to the at least one data unit; forming a plurality ofsegments from the at least one data unit, each one of the plurality ofsegments having the set sequence number as its sequence number,conveying the plurality of segments and the sequence numbers to a targetentity as an earliest data conveyance by using at least one componentcarrier; and determining a master logical radio link control entityoperating on a master component carrier of a plurality of componentcarriers and at least one slave logical radio link control entityoperating on at least one slave component carrier of the plurality ofcomponent carriers, wherein the at least one slave logical radio linkcontrol entity stores the at least one data unit until a segment size isselected and thereafter forming the plurality of segments.
 10. Themethod of claim 9, wherein the forming a plurality of segments is basedon acknowledged mode data (AMD) protocol data unit (PDU) resegmentation.11. The method of claim 10, further comprising: conveying radio linkcontrol (RLC) acknowledged mode data (AMD) protocol data unit (PDU)segments having a same sequence number on different frequency carriers.12. The method of claim 11, further comprising: conveying the radio linkcontrol (RLC) acknowledged mode data (AMD) protocol data unit (PDU)segments having the same sequence number during one subframe.
 13. Themethod of claim 10, further comprising: conveying radio link control(RLC) acknowledged mode data (AMD) protocol data unit (PDU) segmentshaving a same sequence number during several subframes on one componentcarrier.
 14. The method of claim 9, wherein the logical radio linkcontrol entities form a radio link control (RLC) entity defined in the3rd generation partnership project (3GPP) specification.
 15. Anapparatus comprising means for carrying out the method according toclaim
 9. 16. The method according to claim 9, further comprisingselecting a segment size based on a service data unit (SDU) sizerequested by a medium access control (MAC) layer.
 17. At least onememory unit tangibly storing a computer program, the computer programcomprising program code for controlling a process comprising: assigningdata to at least one data unit and set a sequence number to the at leastone data unit; forming a plurality of segments from the at least onedata unit, each one of the plurality of segments having the set sequencenumber as its sequence number, conveying the plurality of segments andthe sequence numbers to a target entity as an earliest data conveyanceby using at least one component carrier; and determining a masterlogical radio link control entity operating on a master componentcarrier of a plurality of component carriers and at least one slavelogical radio link control entity operating on at least one slavecomponent carrier of the plurality of component carriers, wherein the atleast one slave logical radio link control entity stores the at leastone data unit until the segment size is selected and thereafter formingthe plurality of segments.
 18. The at least one memory unit of claim 17,wherein forming the plurality of segments is based on acknowledged modedata (AMD) protocol data unit (PDU) resegmentation.
 19. The at least onememory unit of claim 18, wherein conveying the plurality of segmentscomprises conveying radio link control (RLC) acknowledged mode data(AMD) protocol data unit (PDU) segments having a same sequence numbereither: on different frequency carriers during one subframe, or duringseveral subframes on one component carrier.
 20. The at least one memoryunit of claim 17, the process further comprising selecting a segmentsize based on a service data unit (SDU) size requested by a mediumaccess control (MAC) layer.